The present invention relates to a dashboard clock comprising a liquid crystal plate for providing a display on its front face, a light source for illuminating the rear face of the plate and an electronic control circuit for the plate and the light source.
By way of example, such a clock is utilized on board motor vehicles.
Clocks of this type are already known in which the electronic control circuit is disposed behind and parallel to the plate. In order to make the electrical connections between the circuit and the plate of a reasonable length, the light source, generally a relatively bulky lamp, is placed outside the assembly constituted by the plate and the circuit. A light guide (formed of a transparent material having a refractive index higher than air), one end of which is placed in front of the light source and the other end of which is placed between the circuit and the plate, channels a part of the light from the source towards the rear part of the liquid crystal plate.
However, since only part of the light from the light source is channeled by the light guide, and since this guide has losses, the liquid crystal plate can appear insufficiently lit under certain illumination conditions of the dashboard.
Moreover, if the clock must be utilized in a very cold environment it can be necessary to provide heating means for the liquid crystal plate, which does not function satisfactorily at a temperature lower than a certain limit.